The present invention generally relates to packaging methods for electronic circuit components, particularly to improved carrier tapes for electronic circuit components, and specifically to improved carrier tapes for electronic circuit components for protecting the electronic circuit components in the event that the reel of carrier tape is dropped.
A common packaging method for electronic circuit components such as microchips and utilized in robotic based board assembly is placement into pockets located at precise intervals on a carrier medium. Specifically, such pockets could be arranged in arrays of rows and columns in trays and, especially common for small resistors, capacitors, and memory boards for surface mount assembly of circuit boards, could be arranged in continuous columns in carrier tapes. An example of an advantageous carrier tape is shown and described in U.S. patent appln. Ser. No. 08/631,665 which is hereby incorporated herein by reference.
An example of such an electronic circuit component is the QFP and TQFP product which is a rectangular or square format, thin cross section package with leads extending from all four sides. The leads are spaced in close proximity in the neighborhood of 0.5 mm centers, are 0.2 mm wide by 1 mm long, and are "gull winged" in format. The leads are fragile and must be protected from harsh contact with the carrier tape during transport. Carrier tapes utilize pedestals to support the component in the pocket. Conventional carrier tape confines the body of the component by use of small ridges on or near the pedestals that nest under the gull wing shaped leads and next to the body such that the free ends of the leads of the component are spaced from and ideally do not engage the sidewalls of the pocket. This works well for centering the electronic circuit component in the pocket of the carrier tape.
The IC industry conducts a drop test on the final packaging system which includes carrier tape, cover tape, reel, static control bag, "pizza" box and outer shipping box. It has been reported that 30% of the electronic circuit components sustain damage during drop testing using current tape technology. The mode of failure is lead bending resulting from the rapid deceleration of the electronic circuit components against the near vertical sidewall of the carrier tape pocket after the electronic circuit components "jump" their restraining centering ridges. Specifically, in a drop test, the body of the electronic circuit component "jumps" the centering ridges and the leads of the electronic circuit component collide with the near vertical sidewalls of the carrier tape pocket. Once the body of the electronic circuit component has jumped the ridges, then the ridges can bend the leads. In a drop test of 3 feet, deceleration forces can range from 100 to 10,000 G's depending upon how much deformation one assumes takes place at the box versus at the carrier tape interface. It can be appreciated that the centering ridges of conventional carrier tape pockets do not protect the electronic circuit component from drop damage and in fact are a major source of component failure.
Thus, a need continues to exist in the field of electronic circuit component packaging methods for carrier tape designed to absorb kinetic energy and protect the electronic circuit component from damage and especially protecting the leads of the electronic circuit component from bending, crushing or abrasion.